function open_whiteboard(page) {
	if (!page) {
	  page = 0;
	}
      sendUiMessage("jump" + page);
    document.getElementById('whiteboard_iframe').className = "";
    document.getElementById('whiteboard_table').className = "";
    document.getElementById('whiteboard_cover').className = "";
}

function close_whiteboard() {
    document.getElementById('whiteboard_iframe').className = "hidden_element";
    document.getElementById('whiteboard_table').className = "hidden_element";
    document.getElementById('whiteboard_cover').className = "hidden_element";
}
